Protective sheath assembly for a polymer scaffold

ABSTRACT

A medical device includes a polymer scaffold crimped to a catheter having an expansion balloon. A sheath is placed over the crimped scaffold after crimping to reduce recoil of the crimped polymer scaffold and maintain scaffold-balloon engagement relied on to hold the scaffold to the balloon when the scaffold is being delivered to a target in a body. The sheath is removed by a health professional either by removing the sheath directly or using a tube containing the catheter.

FIELD OF THE INVENTION

The present invention relates to drug-eluting medical devices; moreparticularly, the invention relates to protective sheaths for scaffoldsand stents crimped to a delivery balloon.

BACKGROUND OF THE INVENTION

A variety of non-surgical interventional procedures have been developedover the years for opening stenosed or occluded blood vessels in apatient caused by the build up of plaque or other substances in thewalls of the blood vessel. Such procedures usually involve thepercutaneous introduction of an interventional device into the lumen ofthe artery. In one procedure the stenosis can be treated by placing anexpandable interventional device such as an expandable stent into thestenosed region to expand and hold open the segment of blood vessel orother arterial lumen. Metal or metal alloy stents have been found usefulin the treatment or repair of blood vessels after a stenosis has beencompressed by percutaneous transluminal coronary angioplasty (PTCA),percutaneous transluminal angioplasty (PTA) or removal by other means.Metal stents are typically delivered in a compressed condition to thetarget site, then deployed at the target into an expanded condition ordeployed state to support the vessel.

The following terminology is used. When reference is made to a “stent”,this term will refer to a permanent structure, usually comprised of ametal or metal alloy, generally speaking, while a scaffold will refer toa structure comprising a bioresorbable polymer and capable of radiallysupporting a vessel for a limited period of time, e.g., 3, 6 or 12months following implantation. It is understood, however, that the artsometimes uses the term “stent” when referring to either type ofstructure.

Scaffolds and stents traditionally fall into two generalcategories—balloon expanded and self-expanding. The later type expandsto a deployed or expanded state within a vessel when a radial restraintis removed, while the former relies on an externally-applied force toconfigure it from a crimped or stowed state to the deployed or expandedstate.

Self-expanding stents formed from, for example, shape memory metals orsuper-elastic alloys such as nickel-titanium (NiTi) which are designedto automatically expand from a compressed state when the radialrestraint is withdrawn or removed at the distal end of a deliverycatheter into the body lumen, i.e. when the radial restraint iswithdrawn or removed. Typically, these stents are delivered within aradially restraining polymer sheath. The sheath maintains the lowprofile needed to navigate the stent towards the target site. Once atthe target site, the sheath is then removed or withdrawn in a controlledmanner to facilitate deployment or placement at the desired site.Examples of self-expanding stents constrained within a sheath whendelivered to a target site within a body are found in U.S. Pat. No.6,254,609, US 20030004561 and US 20020052640.

Balloon expanded stents, as the name implies, are expanded uponapplication of an external force through inflation of a balloon, uponwhich the stent is crimped. The expanding balloon applies a radialoutward force on the luminal surfaces of the stent. During the expansionfrom a crimped or stowed, to deployed or expanded state the stentundergoes a plastic or irreversible deformation in the sense that thestent will essentially maintain its deformed, deployed state afterballoon pressure is withdrawn.

Balloon expanded stents may also be stored within a sheath, eitherduring a transluminal delivery to a target site or during the assemblyor in the packaging of the stent-balloon catheter delivery system. Theballoon expanded stent may be contained within a sheath when deliveredto a target site to minimize dislodgment of the stent from the balloonwhile en route to the target vessel. Sheaths may also be used to protecta drug eluting stent during a crimping process, which presses or crimpsthe stent to the balloon catheter. When an iris-type crimping mechanism,for example, is used to crimp a stent to balloon, the blades of thecrimper, often hardened metal, can form gouges in a drug-polymer coatingor even strip off coating through interaction similar to forces at playwhen the blades and/or stent struts are misaligned during the diameterreduction. Examples of stents that utilize a sheath to protect the stentduring a crimping process are found in U.S. Pat. Nos. 6,783,542 and6,805,703.

A polymer scaffold, such as that described in US 20100004735 may be madefrom a biodegradable, bioabsorbable, bioresorbable, or bioerodablepolymer. The terms biodegradable, bioabsorbable, bioresorbable,biosoluble or bioerodable refer to the property of a material or stentto degrade, absorb, resorb, or erode away after the scaffold has beenimplanted at the target vessel. The polymer scaffold described in US2010/0004735, as opposed to a metal stent, is intended to remain in thebody for only a limited period of time. In many treatment applications,the presence of a stent in a body may be necessary for a limited periodof time until its intended function of, for example, maintainingvascular patency and/or drug delivery is accomplished. Moreover, it isbelieved that biodegradable scaffolds, as opposed to a metal stent,allow for improved healing of the anatomical lumen and reduced incidenceof late stent thrombosis. For these reasons, there is a desire to treata vessel using a polymer scaffold, in particular a bioresorbable polymerscaffold, as opposed to a metal stent, so that the prosthesis's presencein the vessel is for a limited duration. However, there are numerouschallenges to overcome when developing a delivery system having apolymer scaffold.

Polymeric materials considered for use as a polymeric scaffold, e.g.poly(L-lactide) (“PLLA”), poly(L-lactide-co-glycolide) (“PLGA”),poly(D-lactide-co-glycolide) or poly(L-lactide-co-D-lactide)(“PLLA-co-PDLA”) with less than 10% D-lactide, and PLLD/PDLA stereocomplex, may be described, through comparison with a metallic materialused to form a stent, in some of the following ways. Suitable polymershave a low strength to volume ratio, which means more material is neededto provide an equivalent mechanical property to that of a metal.Therefore, struts must be made thicker and wider to have the requiredstrength for a stent to support lumen walls at a desired radius. Thescaffold made from such polymers also tends to be brittle or havelimited fracture toughness. The anisotropic and rate-dependant inelasticproperties (i.e., strength/stiffness of the material varies dependingupon the rate at which the material is deformed) inherent in thematerial only compound this complexity in working with a polymer,particularly a bioresorbable polymer such as PLLA or PLGA. Challengesfaced when securing a polymer scaffold to a delivery balloon arediscussed in U.S. patent application Ser. No. 12/861,719 (Attorneydocket 62571.448).

When using a polymer scaffold, several of the accepted processes formetal stent handling can no longer be used. A metal stent may be crimpedto a balloon in such a manner as to minimize, if not eliminate recoil inthe metal structure after removal from the crimp head. Metal materialsused for stents are generally capable of being worked more during thecrimping process than polymer materials. This desirable property of themetal can mean less concern over the metal stent-balloon engagementchanging over time when the stent-catheter is packaged and awaiting usein a medical procedure. Due to the material's ability to be workedduring the crimping process, e.g., successively crimped and released athigh temperatures within the crimp mechanism, any propensity for elasticrecoil in the material following crimping can be significantly reduced,if not eliminated, without affecting the stent's radial strength whenlater expanded by the balloon. As such, following a crimping process thestent-catheter assembly often does not need packaging or treatment tomaintain the desired stent-balloon engagement and delivery profile. Ifthe stent were to recoil to a larger diameter, meaning elasticallyexpand to a larger diameter after the crimping forces are withdrawn,then significant dislodgment force could be lost and the stent-balloonprofile not maintained at the desired diameter needed to deliver thestent to the target site. Consequently, sheaths for metallic stents areoften solely protective, preventing contamination or mechanical damageto the stent and coating. They do not need to be closely fitted toprevent stent recoil on aging and storage.

While a polymer scaffold may be formed so that it is capable of beingcrimped in such a manner as to reduce inherent elastic recoil tendenciesin the material when crimped, e.g., by maintaining crimping blades onthe scaffold surface for an appreciable dwell period, the effectivenessof these methods are limited. Significantly, the material generally isincapable of being worked to the degree that a metal stent may be workedwithout introducing deployed strength problems, such as excessivecracking in the material. Recoil of the crimped structure, therefore, isa problem that needs to be addressed.

In view of the foregoing, there is a need to address the challengesassociated with securing a polymer scaffold to a delivery balloon andmaintaining the integrity of a scaffold-balloon catheter delivery systemup until the time when the scaffold and balloon are delivered to atarget site within a body. Related to these objectives, there is a needto improve the design and handling of a sheath assembly that isremovable (prior to implantation) without causing damage or dislodgmentof the crimped scaffold underneath. There is also a need to improve uponsheaths for, or removal of sheaths from stents.

SUMMARY OF THE INVENTION

The invention is directed to sheaths and/or sheath assemblies used tomaintain a polymer scaffold balloon engagement and delivery systemprofile as well as methods for assembly of a medical device including aballoon expandable polymer scaffold contained within a sheath. Theinvention is also directed to a sheath and methods for applying a sheathand sheath assembly that enables the sheath to be easily removed by amedical professional, e.g., a doctor, so as to minimize disruption to acrimped scaffold-balloon engagement or damage to the crimped scaffold.Sheaths and sheath assemblies according to the invention are removedbefore the medical device is introduced into a mammalian body. Theinvention is further directed to sheaths and their use with stents.

Sheaths according to the invention are particularly useful formaintaining scaffold-balloon engagement and desired delivery profilefollowing a crimping process where the scaffold is crimped down toachieve a smaller crossing-profile, or crimped diameter. A scaffoldformed at a larger diameter, near to or greater than the intendeddeployed diameter, can exhibit enhanced radial strength when supportinga vessel, as compared to a scaffold formed nearer to a crimped diameter.A scaffold formed near to a deployed diameter, however, increases thepropensity for elastic recoil in the scaffold following the crimpingprocess, due to the shape memory in the material. The shape memoryrelied on for enhancing radial strength at deployment, therefore, alsointroduces greater elastic recoil tendencies for the crimped scaffold.Recoil both increases the crossing profile and reduces thescaffold-balloon engagement needed to hold the scaffold on the balloon.In one aspect, the invention is directed to maintaining the crossingprofile and/or maintaining balloon-scaffold engagement for scaffoldsformed near to a deployed diameter.

In another aspect, the invention is directed to a method of assembly ofa catheter that includes crimping a polymer scaffold to a balloon of thecatheter and within a short period of removal of the scaffold from thecrimper placing a restraining sheath over the scaffold. The steps mayfurther include applying an extended dwell time following a finalcrimping of the scaffold, followed by applying the restraining sheath.Both the crimping dwell time and applied restraining sheath are intendedto reduce recoil in the crimped scaffold. The restraining sheath mayinclude both a protecting sheath and a constraining sheath.

In another aspect, the invention is directed to a sterilized medicaldevice, e.g., by E-beam radiation, contained within a sterile package,the package containing a scaffold crimped to a balloon catheter and asheath disposed over the crimped scaffold to minimize recoil of thecrimped scaffold. The sheath covers the crimped scaffold and may extendbeyond the distal end of the catheter to facilitate removal from thescaffold. The sheath may extend at least the length of the scaffoldbeyond the distal end of the catheter. At the distal end of the sheaththere is a portion configured for being manually grabbed and pulleddistally of the catheter to remove the sheath from the catheter.

In another aspect, a medical device is contained within a protectingtube or coil that has a member forming a reduced clearance within thetube lumen. The reduced clearance interferes with a sheath disposed overthe scaffold when the tube is pushed away from a proximal catheter endor the catheter drawn out from a proximal end of the tube. In apreferred embodiment the sheath is a two-piece sheath including aconstraining sheath and protecting sheath portion.

In another aspect, the invention is directed to an apparatus and methodsfor removing a sheath pair from a scaffold in a safe, intuitive mannerby a health professional. According to this aspect of the invention, thesheath pair may be removed by a medical specialist such as a doctorwithout risk of the scaffold becoming dislodged from the balloon ordamaged, such as when the sheath pair is accidentally removed in animproper manner by a health professional.

Sheaths arranged according to the invention provide an effective radialconstraint for preventing recoil in a crimped scaffold, yet arecomparatively easy to manually remove from the scaffold. A sheath thatapplies a radial constraint can be difficult to remove manually withoutdamaging the crimped scaffold, dislodging or shifting it on the balloon.In these cases it is desirable to arrange the sheaths in a manner toapply an effective radial constraint yet make the sheaths capable ofmanual removal in a safe and intuitive manner. By making the sheathremoval process easy to follow and intuitive, the possibility that ahealth professional will damage the medical device when removing thesheath is reduced.

In accordance with the foregoing, there is a scaffold, medical device,method for making such a scaffold, or method for assembly of a medicaldevice (such as a scaffold-balloon catheter assembly) comprising such ascaffold having one or more, or any combination of the following things(1)-(37):

-   -   (1) A one or two piece sheath assembly disposed over a scaffold.        A sheath or sheath portion applies a radial constraint to reduce        recoil of the scaffold. A one-piece sheath applying a radial        constraint is described in FIGS. 5 and 6A-6D of US2012/0324696.    -   (2) Ratio of crimped diameter to balloon nominal inflation        diameter or expanded diameter is greater than about 2, 2.5 or        greater than about 3 or 4; and/or the ratio of pre-crimp        diameter to balloon nominal diameter is about 0.9 to 1.5.    -   (3) The catheter and scaffold are configured as a medical device        suitable for being implanted within a body only after both a        sheath disposed over the scaffold and a tube are removed. The        catheter is not configured for being introduced into the patient        until the sheath pair and/or tube are removed.    -   (4) A scaffold crimped to a balloon and a sheath disposed over        the scaffold. The scaffold is configured for being introduced        into a mammalian body only after the sheath is removed from the        scaffold. And means for removing the sheath from the scaffold.        The scaffold may be at least partially contained within a tube        when the sheath is being removed. The means may include a member        on the tube and/or a sheath configured for being partially or        fully removed before a protecting sheath is removed.    -   (5) A catheter including a sheath over a scaffold. The catheter        is within a tube. And a means for removing the sheath from the        scaffold while the scaffold is at least partially within the        tube.    -   (6) A method of maintaining a low crossing profile or retention        between a scaffold and balloon, comprising: crimping; dwelling        to reduce recoil; placing a first sheath over the scaffold;        removing the first sheath; placing a second sheath; wherein        prior to implantation second sheath is removed    -   (7) A tube having a member that interferes with a sheath when        the sheath is removed from the tube.    -   (8) The protecting sheath is a one or two piece sheath.    -   (9) The tube has a proximal and distal section; the distal        section can be removed from the proximal section to facilitate        crimping or inspection while the catheter remains within the        proximal section.    -   (10) A protecting sheath, when protecting a crimped scaffold,        covers at least the entire length of the scaffold and balloon,        and may extend beyond a distal tip of the catheter by at least a        scaffold length.    -   (11) The protecting sheath has one or two flared, stepped or        notched ends, or no stepped or notched ends.    -   (12) A constraining sheath length that is less, equal to, or        greater than the protecting sheath length.    -   (13) A method for making a sheath includes placing a protecting        sheath within a constraining sheath, and then raising the ends        of the protecting sheath when the protecting sheath is within        the constraining sheath, where the raised ends resist removal of        the constraining sheath from the protecting sheath. The method        may further include attaching a tube to the constraining sheath        to from a two-piece constraining sheath. The constraining sheath        may be longer, the same length or shorter than the protecting        sheath.    -   (14) The sheath may comprise PTFE, PVDF, fluoropolymer,        polyethylene, polypropylene, nylon, nylon copolymers, Pebax,        polyacetal, or polyimide.    -   (15) The polymer comprising the scaffold is bioresorbable, or        the stent comprises a durable, non-bioresorbable, or        non-bioerodible polymer.    -   (16) A constraining sheath has at least a first and second        portion distinguished by their outer diameters—a first outer        diameter corresponding to the first sheath portion that can        apply a radial constraining force on the scaffold, and a second        outer diameter, greater than the first outer diameter,        corresponding to the second sheath portion that is located        distal and/or proximal of the first sheath portion when the        first sheath portion is disposed over the scaffold.    -   (17) A catheter having a sheath wherein the sheath has a        diameter greater than any other part of the catheter, wherein        the catheter when removed from a tube causes the sheath to be        removed while at least part of the catheter remains inside the        tube.    -   (18) A tube includes a member that interferes with a sheath        constraining a scaffold when a catheter supporting the scaffold        is being removed from the tube.    -   (19) The member can be releasably attached to the tube, or        attached to the tube before or after the catheter is inserted        into the tube.    -   (20) Any of the embodiments of structure forming the member        and/or tube 140 having a portion defining the diameter d3 for        interfering with constraining sheath described in connection        with FIGS. 5A-5D and 6A-6B.    -   (21) A member is fitted to, formed in, or attached to a tube        after crimping and sheath placement; and/or the tube has a        separable distal end for access to the balloon during crimping a        sheath placement.    -   (22) A one or two piece tube and catheter with the tube. For the        one-piece tube a member is disposed on the tube after the        catheter (with sheath over scaffold) is within the tube. For the        two piece tube the member may be pre-disposed on the tube before        the catheter including a sheath disposed over a scaffold is        placed within the tube.    -   (23) The member may be disposed at either the proximal or distal        end of the tube.    -   (24) The member interferes with only a sheath disposed over the        scaffold. No other portions of the scaffold, catheter or balloon        are interfered with by the member. They may be freely removed        from the tube without obstruction.    -   (25) An apparatus including a sheath disposed over a crimped        scaffold, the sheath and catheter being disposed within a rigid        tube, the tube's bore defining a clearance that is substantially        less than a diameter of the sheath.    -   (26) The scaffold may be crimped to a balloon catheter, the        catheter may be contained within a tube and the catheter (with        or without the tube) may be contained within an E-beam        sterilized package.    -   (27) Crimping of the scaffold to the balloon includes placing a        one-piece sheath over the scaffold and/or a two-piece sheath        after crimping to reduce recoil.    -   (28) A method of maintaining a low crossing profile or retention        between a scaffold and balloon, comprising: crimping; dwelling        to reduce recoil; placing a first sheath over the scaffold;        removing the first sheath; placing a second sheath; wherein        prior to implantation the second sheath is removed.    -   (29) A method of assembly including placing a catheter within a        first tube wherein only the distal end of the catheter is        outside the tube, crimping; and attaching a second tube to the        first tube to cover the distal end. The tube may include a        clearance at either distal or proximal end.    -   (30) A one or two piece sheath in combination with a stent or        scaffold.    -   (31) A method for maintaining a low crossing profile and/or        retention for a polymer includes crimping a scaffold to a        balloon, placing a first sheath over the crimped scaffold; and        replacing the first sheath with a second sheath; wherein the        crimped scaffold is adapted for being passed through a mammalian        body only after the second sheath is removed. Before or after        replacing the first sheath the scaffold may be placed in a tube        adapted to remove the second sheath.    -   (32) An apparatus including a catheter, the catheter including        including a scaffold comprising a polymer (or a stent comprising        a durable polymer or a metal or metal alloy), the scaffold being        crimped to a balloon; a sheath disposed over the scaffold; a        tube containing at least a portion of the catheter; and a member        disposed within the tube, wherein the member partially or fully        removes the sheath from the scaffold when the tube is separated        from the catheter; and wherein the catheter is configured for        being introduced into a mammalian body only after the sheath is        removed from the scaffold.    -   (33) The apparatus of (32) or (34) or method of (36), in        combination with one of, more than one of, or any combination in        any order of the following list of things: wherein the scaffold        is formed from a radially expanded tube having a pre-crimp        diameter that is at least about 1.5, 2, 3, or 4 times the        crimped diameter of the scaffold; wherein the member is disposed        at an end of the catheter or the tube; wherein the tube is rigid        compared to the sheath; wherein the tube extends substantially        the entire length of a shaft of the catheter; wherein the sheath        includes a constraining portion and a protecting portion, the        constraining portion applying a radial inward force on the        crimped scaffold to limit recoil of the scaffold; wherein the        sheath is a two piece sheath; wherein the sheath includes a        second member that exceeds the clearance, so that the sheath is        partially or fully pulled or pushed off the scaffold when the        second member encounters the clearance; and/or wherein the        member is a clip, rim, flange or portion of the tube.    -   (34) An apparatus for delivery of a medical device, including a        balloon catheter including a balloon having a nominal inflation        diameter; a scaffold formed form a radially expanded tube        comprising a polymer; the scaffold being crimped to the balloon        and having a crimped diameter, wherein the balloon nominal        inflation diameter is about 2, 3 or 4 times greater than the        crimped diameter of the scaffold; a constraining sheath disposed        over the scaffold, the sheath being configured for minimizing        recoil of the scaffold so as to maintain the crimped diameter;        and a rigid tube containing the catheter; wherein the catheter        is adapted for being passed through a mammalian body only after        the catheter is removed from the tube.    -   (35) The apparatus of (32) or (34) or method of (36), in        combination with one of, more than one of, or any combination in        any order of the following list of things: wherein the scaffold        has a morphology characterized by (1) substantially radially        aligned polymer chains resulting from a biaxial expansion of the        scaffold in the radial direction by between about 200 to 400% of        a pre-expansion tube diameter, and (2) the scaffold is crimped        from the tube or pre-crimp diameter to the crimped diameter that        is at least 2-3 times reduced from the tube diameter; wherein        the scaffold is made from a polymer composition comprising PLLA;        wherein the polymer chains of the crimped scaffold are aligned        substantially in a radial direction resulting from a radial        expansion of between about 400% and 450% and axial expansion of        between 150% and 200%, or 10% and 50%; wherein the tube is        configured to partially or fully remove the sheath from the        scaffold, or partially or fully remove a sheath constraining        portion from the catheter when the catheter is withdrawn from a        proximal end the tube; and/or wherein the catheter comprises a        shaft and a hub and wherein the entire shaft is contained within        the tube.    -   (36) A method, including the steps of providing a tube having a        lumen, and contained within the lumen a catheter including a        scaffold crimped to a balloon, wherein a sheath constrains the        scaffold; and removing the sheath from the catheter by removing        the catheter from the tube.    -   (37) The apparatus of (32) or (34) or method of (36), in        combination with one of, more than one of, or any combination in        any order of the following list of things: wherein the tube        extends from at least a catheter distal end to a catheter        proximal end; wherein the scaffold and catheter are configured        for implantation within a body only after both the sheath and        tube are removed; wherein the tube is rigid compared to the        sheath; and/or wherein the removing the sheath step includes        engaging a first member of the tube with a second member of the        catheter.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in the presentspecification are herein incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated to be incorporated by reference. To theextent there are any inconsistent usages of words and/or phrases betweenan incorporated publication or patent and the present specification,these words and/or phrases will have a meaning that is consistent withthe manner in which they are used in the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a polymer scaffold-balloon catheter assemblywith a first pair of sheaths placed over the crimped scaffold. Thesheaths may be removed when the catheter assembly is withdrawn from aprotecting tube.

FIG. 1A shows a side view cross-section of a portion of the device ofFIG. 1 at a proximal end thereof, but with a first constraining sheathreplaced by a constraining sheath as shown in FIGS. 7A-7D.

FIG. 2A is a perspective view of the sheath pair of FIG. 1.

FIGS. 2B-2D show a side view, and first and perspective views of aprotecting sheath of the sheath pair of FIG. 2A.

FIGS. 3A-3D illustrate a method of securing the sheath pair of FIG. 2Ato a distal end of the catheter assembly of FIG. 1.

FIGS. 4A-4C illustrate a method of removing a sheath of FIG. 1 from thedistal end of the catheter assembly of FIG. 1. The catheter assembly iswithin a tube.

FIGS. 5A-5B shows a clip before and after being attached to the tube ofFIG. 1.

FIG. 5C shows a sleeve having a flange. The sleeve is attached to an endof a tube.

FIG. 5D shows a rim formed in a tube.

FIGS. 6A-6B depict a two-piece tube or coil having a neck formed near aproximal end of the tube.

FIGS. 7A-7D depict aspects of a second and third pair of sheaths forconstraining and protecting a scaffold.

FIGS. 8A-8C show a sequence for removal of the sheath pairs of FIGS.7A-7D.

DETAILED DESCRIPTION OF EMBODIMENTS

For purposes of this disclosure, the following terms and definitionsapply:

The term “about” means 20%, 10%, 5%, 2% or 1% less or more than a statedvalue, a range or each endpoint of a stated range, or a one-sigmavariation from a stated mean value. The term “substantially” refers toat least a 30%, 20%, 10%, 5%, 2% or 1% deviation from a value or range.For example, d1 substantially less than d2 means d1 is at least 30%,20%, 10%, 5%, 2% or 1% less than d2.

The term “rigid” is a relative term used to describe something that issubstantially stiffer than some other thing. For example, a first sheathor tube that is radially rigid, rigid in the radial direction, or simplyrigid as compared to a second sheath or tube means that the firstsheath/tube is incompressible compared to the second sheath, oressentially does not deform when an external, radially compressive forceor pinching force is applied as compared to the second sheath, for thesame applied load.

“Inflated diameter” or “expanded diameter” refers to the diameter thescaffold attains when its supporting balloon is inflated to expand thescaffold from its crimped configuration to implant the scaffold within avessel. The inflated diameter may refer to a post-dilation balloondiameter which is beyond the nominal balloon diameter, e.g., a 6.5 mmballoon has about a 7.4 mm post-dilation diameter, or a 6.0 mm balloonhas about a 6.5 mm post-dilation diameter. The nominal to post dilationratios for a balloon may range from 1.05 to 1.15 (i.e., a post-dilationdiameter may be 5% to 15% greater than a nominal inflated balloondiameter). The scaffold diameter, after attaining an inflated diameterby balloon pressure, will to some degree decrease in diameter due torecoil effects related primarily to, any or all of, the manner in whichthe scaffold was fabricated and processed, the scaffold material and thescaffold design.

“Post-dilation diameter” (PDD) of a scaffold refers to the diameter ofthe scaffold after being increased to its expanded diameter and theballoon removed from the patient's vasculature. The PDD accounts for theeffects of recoil. For example, an acute PDD refers to the scaffolddiameter that accounts for an acute recoil in the scaffold.

A “pre-crimp diameter” means an OD of a tube, or the scaffold before itis crimped to a balloon. Similarly, a “final crimped diameter” means theOD of the scaffold when crimped to a balloon and removed from a crimpingmechanism just prior to sheath placement. The “pre-crimp diameter” canbe 2, 2.5, 3.0 times greater than the crimped diameter and about 0.9,1.0, 1.1, 1.3 and about 1-1.5 times higher than an expanded diameter orpost-dilation diameter. A “partial crimp” diameter is a diameterattained after a scaffold or segment is crimped to a diameter less thana pre-crimp diameter and greater than the final crimp diameter. Apartial crimp diameter can be an intermediate diameter after crimpingfrom a pre-crimp diameter to about the nominal or over inflated diameterof the balloon to which the scaffold will be crimped. An example of apartial crimping diameter is described by the scaffold diameterfollowing “Stage II” in FIGS. 3A and 4A, and described in U.S.application Ser. No. 13/644,347 (docket no. 62571.675). A crimpingmechanism or crimper may correspond to a linkage/mechanism includingcooperating blades or teeth configured to apply an approximately uniformradial pressure on a scaffold to reduce its diameter to a final crimpdiameter. The crimping performed by the crimping mechanism may include apolymer material disposed between the teeth and surface of a scaffold;as example of such arrangement being found in US 2012/0042501 (attorneydocket 62571.448).

“Recoil” means the response of a material following theplastic/inelastic deformation of the material and in the absence ofexternally applied forces, e.g., vessel contraction. When the scaffoldis radially deformed well beyond its elastic range and the externalpressure (e.g., a balloon pressure on the luminal surface) is removedthe scaffold diameter will tend to revert back to its earlier statebefore the external pressure was applied. Thus, when a scaffold isradially expanded by applied balloon pressure and the balloon removed,the scaffold will tend to return towards the smaller diameter it had,i.e., crimped diameter, before balloon pressure was applied. A scaffoldthat has recoil of 10% within ½ hour following implantation and anexpanded diameter of 6 mm has an acute post-dilation diameter of 5.4 mm.The recoil effect for balloon-expanded scaffolds can occur over a longperiod of time. Post-implant inspection of scaffolds shows that recoilcan increase over a period of about one week following implantation.Unless stated otherwise, when reference is made to “recoil” it is meantto mean recoil along a radial direction (as opposed to axial or alonglongitudinal direction) of the scaffold.

“Acute Recoil” is defined as the percentage decrease in scaffolddiameter within the first about ½ hour following implantation within avessel.

“Axial” and “longitudinal” are used interchangeably and refer to adirection, orientation, or line that is parallel or substantiallyparallel to the central axis of a stent or the central axis of a tubularconstruct. The term “circumferential” refers to the direction along acircumference of the stent or tubular construct. Thus, a link spaced 180degrees from another link means 180 degrees as measured about thecircumference of the tubular construct.

“Radial” refers to a direction, orientation, or line that isperpendicular or substantially perpendicular to the central axis of thestent or the central axis of a tubular construct and is sometimes usedto describe a circumferential property, i.e. radial strength.

A polymer scaffold according to a preferred embodiment is formed from aradially expanded or biaxially expanded extruded PLLA tube. The degreeof radial expansion (RE) and axial expansion (AE) that the polymer tubeundergoes can characterize the degree of induced circumferentialmolecular and crystal orientation as well as strength in acircumferential direction. In some embodiments the RE is about 400% andthe AE is 40-50%. Other embodiments of processing parameters, RE and AEexpansions considered within the scope of the disclosure are found inU.S. application Ser. No. 13/840,257 filed Mar. 15, 2013 (AttorneyDocket 104584.47).

The scaffold is laser cut from the expanded tube. The diameter of thetube is preferably selected to be about the same, or larger than theintended deployed diameter for the scaffold to provided desirable radialstrength characteristics, as explained earlier. The scaffold is thencrimped onto the balloon of the balloon catheter. Preferably, aniris-type crimping mechanism is used to crimp the scaffold to theballoon. The desired crimped profile for the scaffold is ½ or less than½ of the starting (pre crimp) diameter of the expanded tube andscaffold. In the embodiments, the ratio of the starting diameter orpre-crimp diameter to the final crimp diameter may be 2:1, 2.5:1, 3:1,or higher and the pre-crimp diameter may be about 0.9 to about 1.5higher than the balloon nominal inflation diameter. The ratio ofpre-crimp or intermediate crimp diameter to final crimped diameter maybe greater than a ratio of expanded or post-dilation diameter to thefinal crimped diameter of the scaffold.

The pre-crimp memory in the scaffold material following crimping willinduce some recoil when the scaffold is removed from the crimper. Whilea dwell period within the crimper can reduce this recoil tendency, thereis residual recoil to restrain while the scaffold awaits use. This isdone by placing a restraining sheath over the scaffold after the crimperblades are released and the scaffold removed from the crimper head. Thisneed to reduce recoil is particularly evident when the diameterreduction during crimping is high, e.g., as in above examples, since fora larger starting diameter compared to the crimped diameter the crimpedmaterial can have higher recoil tendencies. Examples of polymers thatmay be used to construct sheaths described herein are Pebax, PTFE,polyethylene, polycarbonate, polyimide and nylon. Examples ofrestraining sheaths for polymer scaffold, and methods for attaching andremoving restraining sheaths for polymer scaffold are described inUS20120109281, US20120324696 and U.S. Pat. No. 8,414,528, and U.S.application Ser. No. 13/708,638 (docket no. 62571.676).

FIG. 1 shows a side view of a distal portion of a scaffold-ballooncatheter assembly 2. The catheter assembly 2 includes a catheter shaft 4and a scaffold 10 crimped to a delivery balloon 12. As shown there aretwo separate sheaths 20, 30 disposed over the scaffold 10. The scaffold10 is contained within a protecting sheath 20 and a constraining sheath30, which is slid over the outer surface of the protecting sheath 20 toposition it over the scaffold 10. Before inserting the catheter assembly2 distal end within a patient, both the constraining sheath 30 andprotecting sheath 20 are removed by a health professional.

The sheaths 20, 30 provide an effective radial constraint for reducingrecoil in the crimped scaffold 10. Yet the sheaths 20, 30 are alsoeasily removed by a health professional at the time of a medicalprocedure by pulling or pushing the outer sheath 30 towards the distalend of the scaffold 10 and balloon 12 using a tube, within which is thecatheter assembly 2. This aspect of the disclosure (involving a tube) isdescribed in more detail later. The removal technique for sheaths 20, 30includes a similar motion to the removal technique required for othercoronary device products, where a single, non-constraining sheath isused to cover and protect the stent. In those cases the sheath isgrasped by the doctor or technician's gloved hands and pulled offtowards the distal end of the device. But, as described herein, a sheaththat applies a radial constraint can be difficult to manually removewithout adversely affecting the structural integrity of the medicaldevice. In these cases, it is desirable to arrange the sheaths so thatspecial handling is not required by the health professional when thesheath is manually removed. By making the sheath removal process easy tofollow or intuitive, the possibility that a health professional willdamage the medical device by improperly removing the sheath is reduced.

The constraint imposed by the sheaths 20, 30 maintain the scaffold 10 atessentially the same, or close to the same diameter it had when removedfrom the crimping mechanism. The sheath 30 is tightly fit over thesheath 20 and scaffold 10 so that the radial inward force applied on thescaffold 10 can prevent or reduce recoil in the scaffold 10. The healthprofessional may then remove both sheaths at the time of the medicalprocedure. As such, any potential recoil in the scaffold 10 prior tousing the medical device is minimized.

The sheath 30, although imposing a tight fit on the scaffold 10 (throughsheath 20), can be easily removed by a health professional without riskof the scaffold 10 being accidentally pulled off of the balloon 12. Thismay be done in a number of ways according to the disclosure; at leastone of the ways based on the manner in which the sheath 20 is positionedand removed from the scaffold 10. If there are excessive pulling forceson the scaffold 10 when sheaths are removed, the catheter shaft 4 may bedamaged, the scaffold 10 may dislodge from a balloon 12, or shift on theballoon 12; thereby reducing scaffold-balloon engagement relied on tohold the scaffold 10 to the balloon 12.

When the scaffold 10 is constrained by sheath 30, as in FIG. 1, theconstraining sheath 30 is located over the section of the protectingsheath 20 where the crimped scaffold 10 is found. This sheath 30 is madefrom a polymer tube material having a thickness and pre-stressed innerdiameter size suitably chosen to cause the sheath 30 to apply a radiallyinward directed force on the scaffold 10. The thicker the tube and thesmaller the pre-stressed inner diameter size for the sheath 30 thehigher this constraint will be on the scaffold 10. However, the sheath30 thickness should not be too thick, nor its inner diameter too smallas this will make it difficult to slide the sheath 30 over, or removethe sheath 30 from the scaffold 10. If excessive force is needed toreposition the sheath 30, the scaffold 10 can dislodge from the balloon12 or the scaffold 10 and catheter shaft 4 can become damaged when thesheath 30 is moved.

If only sheath 30 were applied, i.e., the sheath 20 is not present, theamount of preload that the sheath 30 could apply to the scaffold 10without affecting scaffold-balloon engagement would be limited. However,by introducing the protecting sheath 20 between the scaffold-balloonsurface and sheath 30 the sheath 30 can impose a higher preload on thescaffold 10 without risk to the integrity of the scaffold-balloonengagement when the sheath 30 is applied to and/or removed from thescaffold 10. The protecting sheath 20 therefore serves to protect theintegrity of the scaffold-balloon structure as the sheath 30 isrepositioned relative to the scaffold 10. An example of a one-piecesheath that is capable of performing in a similar manner is found inUS2012/0324696 at FIGS. 5 and 6A-6D.

The protecting sheath 20 extends over the entire length of the scaffold(as shown) and beyond the distal tip of the catheter assembly 2 (as canbe seen in FIG. 3B) may the sheath 20 extend. The protecting sheath 20is preferably formed from a unitary piece of polymer material, which isshaped to form differently sized portions 22, 24 and 25 for protectingthe scaffold/balloon 10/12.

At the distal end 20 b of sheath 20 there is a raised end 22 in the formof a cylinder section having a larger diameter than the body portion 21of the sheath 20 to the right of end 22 which covers the scaffold 10 inFIG. 1. Raised end 22 provides an abutting surface with respect todistal movement of sheath 30, i.e., end 30 b of sheath 30 abuts end 22when sheath 30 is moved to the left in FIG. 1. End 22 may alternativelytake the shape of a cone with the largest diameter end of the cone beingthe most distal end of the sheath 20. The raised end 22 may function toremove the sheaths 20, 30, as explained below.

The protecting sheath 20 has a cut 26, extending from the proximal end20 a to a location about at the distal the tip of the catheter assembly2 (or sheath 20). The cut 26 forms an upper and lower separable halve28, 29 of the sheath 20 (FIG. 2D). These halves 29, 28 are configured tofreely move apart when the sheath 30 is positioned towards the distalend 20 b. The location 26 a may be thought of as a living hinge 26 aabout which the upper half 29 and lower half 28 of the sheath 20 canrotate, or deflect away from the scaffold 10. When sheath 30 is moveddistally of the scaffold 10 in FIG. 1, the halves 28, 29 will tend toopen up naturally, due to the preload applied by sheath 30 near hinge 26a (the separable halves 28, 29 can be more clearly seen in FIGS. 2A-2D).This arrangement for halves 29, 28 provides easy removal of sheath 20from the scaffold 10, with minimal disruption to scaffold-balloonstructural integrity, after sheath 30 is moved towards distal end 20 b.When sheath 30 is being fitted over the scaffold 10 or removed from thescaffold 10, the presence of the halves 28, 29 prevent direct contactbetween the sliding sheath 30 and the surface of the scaffold 10.

Sheath 20 may alternatively be formed as two completely separablehalves, e.g., as halves 145a and 140a illustrated in FIG. 11C ofUS2012/0324696 or as the same two halves shown in FIG. 2 but with thecut 26 running the length of, or substantially the entire length of thesheath 20. In the case of the former sheath 20 embodiment, sheath 150 ofFIG. 11C of US2012/0324696 is replaced by the sheath 30 illustrated inFIG. 1 or other suitable embodiments thereof, discussed more fullybelow.

FIG. 1A shows a proximal end 20 a of sheath 20 with another embodimentof a constraining sheath—an outer sheath 230 (see FIGS. 7A-7C)—disposedover the sheath 20. Referring to FIG. 1A, at the proximal end 20 a thereare portions 24 and 25 formed when the combined proximal ends of halves28, 29 are brought together as in FIG. 1. When the halves 28, 29 arebrought together notch portion 25 and raised (or stepped) portion 24,similar to end 22, are formed. The notched portion 25 has an outerdiameter less than the inner diameter of the portion 21 of the sheath30/230 that covers the scaffold 10, as well as the outer diameter of thescaffold/balloon 10/12. The raised portion 24 has a diameter greaterthan the body portion 21, which refers to the inner diameter of thesheath 30 or sheath 230 in FIG. 1A and the diameter for end 24 may bethe same as the diameter for end 22. The raised portion 24 provides anabutment or stop 24 a preventing a proximal end 30 a of the sheath30/230 from moving to the right in FIG. 1. The portion 24 may preventthe sheath 30/230 from sliding off of the scaffold 10 and/or locate theportion of end 30 a of sheath 30/230 relative to sheath 20 proximal end20 a so that sheath 30/230 applies a uniform compressive force over theentire length of the scaffold. A compressive portion of the sheath30/230 (discussed below) has a length about equal to the length of theportion 25 plus the scaffold/balloon length so that when end 30 a abutsend 24 the sheath 30 will properly cover the entire scaffold/balloon10/12 length.

Portion 25 discourages removal of the sheath 20 prior to removal ofsheath 30 from the scaffold 10. Referring again to FIG. 1A, there is aclose-up of the proximal end 20 a with the sheath 230 (shown in phantom)replaced by the inwardly directed preload F30 it applies to sheathportion 21 when positioned over the scaffold 10. A distal end of portion25 forms a ledge 25 a. When sheath 30 is positioned over the scaffold 10the inwardly directed preload F30 applied to sheath portion 21 urges thehalves 29, 28 together. With the halves 28, 29 urged together, thescaffold/balloon proximal end 14 a blocks movement of the sheath 20 tothe left in FIG. 1A by interfering with the movement of the ledge 25 ato the left. Thus, if a user attempts to pull the sheath 20 off prior toremoving the sheath 230/30 from the scaffold 10 area (which can damagethe scaffold/balloon integrity or catheter shaft 4), there will beresistance to this movement due to the ledges 25 a abutting the balloonproximal end 14 a (the ledge 25 a thus may be thought of as aninterference or interfering ledge part of the sheath 20). Thisresistance should indicate to the user that the sheaths 20, 30/230 arebeing removed in an improper manner. When the sheaths 20, 30/230 areremoved properly, the first sheath 30 is moved to the distal end 20 b ofthe sheath 20 (thereby removing the preload F30) so that the halves 28,29 freely open up to allow the ledge 25 a to easily pass over thescaffold 10 so that sheath 20 is removed without resistance. The user isthereby informed that the sheath 20 is removed properly when there is noresistance to removing the sheath 20 from the balloon-catheter assembly2.

Thus, scaffold-balloon integrity is protected by the presence of thehalves 28, 29 and the notched portion 25, as discussed above. Theextended length of sheath 20, beyond the tip of the catheter assembly 2,e.g., is about equal to a length of the scaffold 10, the length of thesheath 30 or greater than both. This length beyond the distal tipfacilitates an intuitive sliding removal or attachment of the sheath 30from/to the scaffold 10 by respectively sliding the sheath 30 along thesheath 20 extension that is beyond the distal tip of the catheterassembly 2. The length of the sheath 20 that extends beyond the distalend of the catheter assembly 2 (length L21 in FIG. 4A of US2012/0324696)may depend on the choice of sheaths used. For example, from theperspective of the health professional removal process, if the sheath 20is more stiff (e.g., higher wall thickness and/or modulus) relative tothe sheath 30 then the length beyond distal end 4 for sheath 20 may belonger so that the halves 28, 29 of sheath 20 can be more safelydisplaced from the scaffold 10 by clearing the sheath 30 more distallyof the scaffold 10. If the sheath 30 wall thickness and/or modulus ishigher relative to sheath 20 than the length may be shorter since thesheath 30 will tend to naturally open up the halves 28, 29 as it ismoved distally of the distal tip of the catheter assembly 2. Also, athicker or higher modulus sheath 20 and/or sheath 30 may be desirable toincrease the resistance to improper removal of sheath 20, e.g., as whena user attempts to remove sheath 20 with, or before removing sheath 30from the scaffold 10 (as discussed earlier).

In a preferred embodiment the constraining sheath is made with a portionhaving a diameter greater than the diameter of other portions of theconstraining sheath. When sheath 30 is positioned on a scaffold, as inFIG. 1, member 130 may define a diameter substantially greater than anyother diameter along the length of the catheter portion received withina protecting tube or coil.

In one example, adjacent to, or at proximal end 30 a of sheath 30 inFIG. 1 there is a raised portion 130 having a diameter d1. The diameterd1 is selected so that the sheath 30 is engaged by, or makes contactwith a member disposed on a tube (or coil) when the catheter assembly 2is being removed from the tube, as illustrated in FIGS. 4A-4C (discussedin more detail below). The portion 130 may be formed from the samematerial as sheath 30, e.g., start with a tube of diameter d1 and reduceor step-down to the diameter of the constraining portion of sheath 30(FIG. 1) while leaving portion 130 at the original diameter d1. Theportion 130 may be raised, flared out, or frusto-conical in shape, or aseparate piece attached to the sheath 30 to form 130. The length ofportion 130 may be such that when end 30 a is abutting portion 24 theentire scaffold is receiving a uniform compressive force. In thisregard, for a portion 130 formed by a flared out or raised in/outportion of the same tube used to form sheath 30, the portion 130 isproximal of the sheath 30 so that a uniform compressive force is appliedover the entire length of the scaffold 10. In other embodiments—e.g., awelded annular piece forming the diameter d1, or 2, 3, 6,circumferentially-spaced tabs each forming an extent for sheath 30 equalto d1 when attached to the outer surface of sheath 30—the portion 130may be located over the scaffold when sheath 30 is constraining thescaffold without affecting the radial compressive force anywhere overthe scaffold length.

Referring to FIGS. 2B-2D, there are shown various views of the sheath20. FIG. 2A shows the sheath 20 with the sheath 30. The constrainingportion of sheath 30 referred to earlier, may have the length L30 suchthat sheath 30 applies a sufficiently uniform radial inward force orpreload on the scaffold 10 when end 30 a abuts end 24 a (FIG. 1A). Thelength L30 is slightly greater than the length of the scaffold-balloonstructure. The sheath 30 can be slid towards or away from the scaffoldlocation (i.e., its location in FIG. 2A or FIG. 1) over the sheath outersurface 20. As noted earlier, the sheath 20 has separable upper andlower halves 29, 28 formed by a cut 26 made across the tube formingsheath 20. FIG. 2D is a perspective view of the upper and lower halves28, 29 separated from each other. As can be appreciated from this view,the halves 28, 29 rotate about the hinge 26 a when they separate. FIGS.2B and 2C show an additional side and perspective view, respectively, ofthe sheath 20 showing the aforementioned structure, including theportions of notched or stepped portion 25 and end 24 (FIG. 1A) discussedearlier.

The length L20 in FIG. 2C may extend over the scaffold 10 length as wellas a sufficient distance beyond the scaffold 10 so that the sheath 30can be pushed onto the scaffold 10, and removed from the scaffold 10while the halves 28, 29 are disposed over the scaffold 10. The lengthL20 may be at least twice the length of sheath 30, i.e., L20=2*L30, toachieve this purpose. This length should be sufficient to allow theupper and lower halves 28, 29 to peel or rotate about the living hinge26 a and freely away from the scaffold surface (as in FIG. 2D) withoutinterference from the sheath 30 when sheath 30 abuts end 22.

As mentioned earlier, a thicker tube and smaller inner diameter forsheath 30 will cause the sheath 30 to apply a greater pre-load on thescaffold 10. The sheath 30 thickness and/or inner diameter size isselected with the sheath 20 in mind. That is, the sizing of one candetermine what sizing to use for the other, based on achieving anappropriate balance among the amount of pre-load desired, the ease inwhich the sheath 30 can be placed over or removed from the scaffold 10location, increasing resistance to improper removal of sheath 20 (ledge25 a abutting proximal end 14 a, as discussed above) and avoidingdisruption to the integrity of the scaffold-balloon structure, e.g.,pulling the scaffold 10 off the balloon when the sheath 30 is beingremoved. For example, if a relatively thin and/or low modulus tube isused for sheath 20 (as compared to sheath 30), the sheath 30 will imposea higher localized pre-load on the scaffold 10. And the scaffold 10 ismore likely to be affected by sheath 30 movement because the sheath 20easily deforms under the movement of the sheath 30. If the sheath 20 ismade thick and/or a higher modulus tube material is used for sheath 20(compared to sheath 30) the scaffold 10 will not be as affected bymovement of the sheath 30. And local changes in pre-load on the scaffold10 will tend to be lower since the sheath 20 does not deform as easilyunder the movement of the sheath 30.

Referring to FIGS. 3A-3D, methods of assembly of a medical deviceaccording to some aspects of the disclosure are now described. Themedical device, in its assembled state according to some aspects of thedisclosure, includes the scaffold crimped to a balloon catheter, the twopiece sheath disposed over the scaffold as in FIG. 1, and the catheterbeing contained within a protecting tube. The aspects of the protectingtube (or coil) are discussed in greater detail below in connection withFIGS. 4A-4C, 5A-5D and 6A-6B.

The catheter assembly 2 with sheaths arranged as in FIG. 1 and containedwithin a protecting tube is packaged and sterilized. At the time whenthe catheter assembly is to be used in a medical procedure the packageis opened and the tube and sheath pair removed. According to anotheraspect of the disclosure the catheter assembly 2 is not configured forbeing introduced into the patient until a sheath or sheath pair, e.g.,sheath 30/230, is removed. Examples follow.

After (or before) placing the catheter within the tube, and before thesheaths 20/30 are placed, the scaffold 10 is crimped to the balloon 12of the catheter assembly 2 using a crimping mechanism. As noted above,for a polymer scaffold the diameter reduction during crimping may be2:1, 2.5:1, 3:1, 4:1 or higher. The scaffold may be placed on a balloonhaving a nominal, expanded or post-dilation diameter that is about 2,2.5., or 3 times the diameter of the scaffold when the scaffold has afinal crimp diameter on the balloon.

The diameter reduction (from a pre-crimp size to the final crimpdiameter) introduces high stresses in the scaffold structure. The memoryin the material following crimping causes recoil of the scaffoldstructure, as discussed earlier; one can incorporate lengthy dwell timeswithin the crimper, e.g., after the final crimp step, to allowstress-relaxation to occur in the structure while heated crimper bladesare maintaining a fixed diameter and temperature to facilitate stressrelaxation. Both the dwell period and the imposition of a constrainingsheath over the crimped scaffold after crimping helps to reduce recoilafter crimping. Crimping of the scaffold 10 to the balloon 12 includingdesirable dwell times and temperatures that can affect stress relaxationand recoil after crimping are disclosed in U.S. patent application Ser.No. 12/861,719 (docket no. 62571.448), U.S. patent application Ser. No.13/089,225 (docket no. 62571.517) and U.S. patent application Ser. No.13/107,666 (docket no. 62571.522).

Following removal from a crimping mechanism the scaffold will recoilunless subject to a radial constraint. According to one aspect of thedisclosure a temporary one-piece sheath is placed on the scaffoldimmediately following crimping, then replaced by the sheath of FIG. 1after about ½ hour from removal from the crimping mechanism. Examples ofthe one-piece sheath according to the disclosure is one-piece sheath 23described in U.S. application Ser. No. 13/708,638 (docket no.62571.676).

The sheath pair 20/30 may be attached as follows. The sheath pair, shownin FIG. 3A, is placed on a mandrel 8 before being attached to thecatheter assembly 2. The mandrel 8 is passed through the catheter shaft4 guidewire lumen (not shown), and exits at the distal end of thecatheter assembly 2. The sheath pair is then placed on the mandrel 8distally of the catheter assembly 2. The mandrel 8 may then be used toguide the sheath pair over the scaffold-balloon 10/12 as illustrated inFIGS. 3B-3D.

Referring to FIG. 3B, the distal end 30 b of the sheath 30 is adjacentto the raised end 22 of the sheath 20. In this configuration the halves28, 29 can freely open or close. The sheath pair is then brought towardsthe scaffold-balloon 10/12. The halves 28, 29 easily deflect over thescaffold-balloon 10/12. The sheath pair may be slid towards thescaffold-balloon 10/12 as follows. Holding the catheter assembly 2stationary, grasping the mandrel 8 with one hand and the sheath pairwith the other hand and sliding the sheath pair over the mandrel 8 untilthe halves 28, 29 are located over the scaffold-balloon 10/12 as shownin FIG. 3C. When properly positioned, the portions 24, 25 are positionedwith respect to proximal end 14 a as shown in FIG. 1A.

Referring to FIGS. 3C-3D, once the halves 28, 29 are located properlyover the scaffold-balloon 10/12 to protect this structure, theconstraining sheath 30 can be pushed over the scaffold-balloon 10/12 (asindicated in FIGS. 3C-3D by P). The sheath 30 may be pushed over thescaffold-balloon 10/12 in the following manner. The raised end 22 andmandrel 8 are grasped with one hand to hold the two stationary. Then,using the other hand the sheath 30 is pushed over the scaffold-balloon10/12 until the end 30 a of sheath 30 is disposed adjacent to, or abutsthe raised end 24 of the sheath 20, which indicates the proximatelocation of the proximal end 14 a (FIG. 1A) of the balloon-scaffold10/12. Alternatively, the portion 24 and catheter shaft 4 may besimultaneously held with on hand, while the sheath 30 is pushed towardsthe scaffold 10 with the other hand. By grasping the portion 24 with thecatheter shaft 4, the halves 28, 29 are held in place relative to thescaffold 10 while the sheath 30 is being pushed over the scaffold 10.

With the sheath positioned over the scaffold as in FIG. 1, the catheteris placed within a tube or coil. The tube or coil, which may be rigidcompared to the catheter shaft, protects the catheter duringshipment/delivery and storage. When the packaged and sterile medicaldevice is received by a health professional, it may be enclosed within arigid tube to protect the contents inside from damage.

According to another aspect of the disclosure, the tube or coil is fitwith, or includes a member for removing a sheath or sheaths from thescaffold as the catheter is removed from the tube or coil. Moregenerally, there is a structure including a tube and a member thatinterferes with a sheath constraining a scaffold when a cathetersupporting the scaffold is being removed from the tube.

Referring to the example of FIG. 4A-4C, there is shown a sequence ofevents during removal of the catheter 2 from a tube 140. The tube has aclearance d2, which is larger than the diameter d1 of the member 130. Assuch, for the tube 140 having a clearance d2 everywhere long the tube'slumen, the catheter freely slides along the tube without interferencefrom the tube. According to another aspect of the disclosure a member152 interferes with the catheter 2 removal from the tube 140, resultingin one or more sheaths being removed from the scaffold 10 when thecatheter 2 is removed from the tube 140. The member 152 (described ingreater detail below) forms a reduced clearance d3, which is less thand1 and d2.

A member may be disposed near a proximal or distal end of a tube orcatheter. Preferably, the member 152 is located near the catheterproximal end (i.e., adjacent the catheter hub) when the catheter iswithin the tube 140. Referring again to FIGS. 4A-4C, during its removalsequence the catheter 2 is withdrawn from the tube 140 proximal end (notshown) or the tube 140 pushed towards the catheter 2 distal end whilethe catheter proximal end is held. In either case, the member 152 iseventually is brought near the member 130 of sheath 30 and begins topush sheath 30 towards a distal end of sheath 20 or the distal end ofthe catheter 2. FIG. 4C shows the sheath 30 displaced to the left andalmost completely removed from the scaffold 10. This action leaves onlythe inner sheath 20 halves 28/29 remaining over the scaffold 10. Afterthe catheter 2 has been removed from the tube 140 the sheath 20 may beeasily removed from the scaffold 10 (since sheath 20 does not apply acompressive force on the scaffold 10). In the case of a raised end 22for sheath 20, FIG. 1, the continued movement of sheath 30 to the leftin FIG. 4C by member 152 may also remove sheath 20 from scaffold 10 (asexplained in greater detail in connection with FIGS. 4A-4C of U.S. Pat.No. 8,414,528). Alternatively, the sheath 20 can be partially or fullymaintained in its position over the scaffold 10 after removal of thecatheter from the tube 140. And the sheath 30 may be partially retainedon the sheath 20 and/or the catheter after removal from the tube 140.Thus, after the catheter is removed from the tube, the sheaths 20/30 maybe fully or partially removed from the scaffold 10 and/or catheter.

Embodiments of structure defining clearance d3 for interfering with asheath are now described in connection with FIGS. 5A-5D and 6A-6B.

Referring to FIGS. 5A-5B, a clip 150 is placed near a proximal end ofthe tube 140. The clip may be formed by two halves 150 a, 150 bconnected to each other through a living hinge 153. Each half 150 a, 150b has a protrusion 152. The tube 140 is modified to provide two oppositethrough-holes 143 for passage of protrusions 152 into the bore of thetube 140 when the clip halves 150 a, 150 b are brought together, asillustrated in FIGS. 5A-5B. There is a clearance d3 between the ends ofthe protrusions 152. The clip may be held together by a fastener 156,such as adhesive, ultrasonic welding, solvent bonding, tape, cable tieor tie wrap.

Referring to FIG. 5C there is a sleeve 150′ that has an inner flange152′. The flange forms a reduced clearance d3. The inner surface of thesleeve 150′ is sized to snugly receive the tube 140 so that the proximalend abuts the flange 152′. The sleeve 150′ may be fastened to theproximal end of the tube 140 to provide the member in the tube 140 forinterfering with the removal of the catheter 2 from the tube; that is,removing at least sheath 30 from the scaffold 10. The catheter 2, priorto crimping or prior to sheath placement, is fed into the end of sleeve150′ with tube 140 fitted at the opposite end of sleeve 150′.

Referring to FIG. 5D a rim 150″ forming an inner surface 152″ may beformed in the tube 140. The inner surface 152″ provides a decrease inclearance from d2 to d3 near the proximal end of the tube 140. The rim150″ is formed by re-shaping an end of a tube having an inner diameterd2. Such reshaping may be accomplished by swaging or applying acombination of heat and pressure.

FIGS. 6A-6B depict aspects of a tube 160 for receiving the catheter 2according to another aspect of the disclosure. In one respect the tube160 provides another embodiment of structure forming the member forinterfering with a sheath. Referring first to FIG. 6B, which refers tothe proximal end 165 of the tube 160, the diameter is stepped down fromd2 to d3. The d3 clearance may extend over a length L (L can be aboutless than or equal to the length of the sheath 30/230) to provide anarrowed passage or neck 150′″ with clearance d3 between walls 152′″.

Referring to FIG. 6A the tube 160 is formed by a first tube portion 160a, which includes the proximal end 165 of the tube 160, and a secondtube portion 160 b, which includes the distal end 166 of the tube 160.The portions 160 a and 160 b are separate pieces of the tube 160. Asleeve, tape or clip 168 may be used to fasten the two pieces together.When the catheter and scaffold (radially constrained by a sheath) areassembled the catheter shaft and distal end portion are contained withinthe tube 160. The handle or hub portion of the catheter (not shown) isexternal to the tube 160 and adjacent the tube 160 proximal end 165. Asindicated in FIG. 6A the neck 150′″ is located near the proximal end165. The catheter is removed from the tube 160 by pulling the handle orhub portion (e.g., the catheter portion having a steering and/or lumenpressure control) away from the tube proximal end 165 or pushing thetube towards the catheter distal end. In either case the neck 150′″interferes with a sheath, constraining sheath or outer sheath, e.g.,sheath 30, but not any other portion of the catheter.

Tube 160 has a separable piece 160 b for purposes of processing orassembly of the catheter distal end while the remaining portion of thecatheter is contained within the tube portion 160 a. The portion 160 bof the tube 160 has a length at least equal to the length of thecatheter distal portion including the balloon. With the portion 160 bdetached from the portion 160 a an operator may have free access to theballoon 12 for crimping, inspection and/or affixing one or more sheathsto the crimped scaffold without having to remove the remainder of thecatheter from the tube 160. As such, a majority of the catheter mayremain within the protective tubing configured to a remove a sheath,thereby preventing inadvertent damages to the catheter shaft duringprocessing, while a distal end including a scaffold and balloon may beinspected, a scaffold crimped to a balloon and a sheath placed over thescaffold.

The operator may place the sheath, e.g., sheath 20/30, having a memberdefining the d1 diameter on the crimped scaffold while the catheterremains in the tube portion 160 b. After attaching the sheath, e.g.,sheath 20/30 of FIGS. 1-2, to the scaffold, the portion 160 b may beaffixed to the portion 160 a using the sleeve 168. If the detachableportion 160 b were not provided, then the catheter could not be placedwithin the tube 160 since the neck 150′″ defining clearance d3 woulddisrupt the constraining sheath when the catheter is placed within thetube. For a one-piece tube the structure 150, 150′, 150″ or 150′″ may befitted to, formed in, or attached, respectively, to the tube aftercrimping and sheath placement (since the hub, handle or handle portionof the catheter is fixed at the proximal end of the shaft, the cathetershaft may only be placed within the tube from the tube proximal end165). According to the embodiment of FIG. 6A, the neck 150′″ may beformed in the tube and catheter placed within the tube 160 prior tocrimping and sheath placement. After sheath placement the portion 160 bcan be re-attached.

With reference to FIGS. 7A-7D and FIGS. 8A-8C, now described are sheathsaccording to other aspects of the disclosure.

Referring to FIGS. 7A-7C, as an alternative to sheath 20/30 depicted inFIGS. 1-2 and described earlier, a modified sheath 230 replaces thesheath 30. Sheath 230 differs from sheath 30 in the following manner.Sheath 230 does not include the member 130 and sheath has an expandedportion that may be gripped by a user without also pulling on theprotecting sheath 20 during sheath removal. The sheath 20/230 (FIGS.7A-7B) facilitates a more safe removal of the constraining sheath bypreventing, prior to, or current with, removal of the sheath 230 theprotecting sheath 20. Removing both sheaths at the same time can damagethe scaffold or catheter, as discussed above. The preferred removal isto remove sheath 20 only after a constraining sheath 230 has cleared thescaffold.

By providing the extension 240 having a length L240 (as opposed tosheath 30 having a total length L30) a user is discouraged from grippingthe sheath 20, since the extension 240 is disposed over about theentirety of sheath 20 (thereby making it difficult to pull on sheath 20directly). The sheath 230 includes a portion 240 and 235. The portion240 may have a larger outer diameter than the portion 235. The sheath230 may be formed from a single tube with diameter of the portion 240.The portion 235 is formed as stepped-down part of the tube 230 and haslength L30. The portion 235 applies the radially compressive force onthe scaffold 10. The total length of the sheath 230 is L230, which isequal to the sum of L30 and L240. The length L230 may be about orslightly less than the length of sheath 20, such that both ends 24 and22 of sheath 20 are visible when sheath 230 is disposed over sheath 20.

A method of removal of the sheath 20/230 from the scaffold 10 is nowdescribed. At the time when the catheter assembly is to be used in amedical procedure the package is opened and the sheath pair removed fromthe distal end. The catheter assembly 2 is not configured for beingintroduced into the patient until the sheath pair is removed. FIG. 8Adepicts the arrangement of the sheaths 20, 230 at the distal end of thecatheter assembly 2 when the packaged and sterile medical device isreceived by a health professional. Examples of such sterile packaging isfound in U.S. patent publication no. US 2008-0010947 (docket no.62571.60). The sheath 20 and portion 240 may extend well-beyond thedistal end of the catheter 2 assembly such that they overhang thecatheter distal end by about the length of the scaffold or length L30.These overhanging portions are provided to facilitate an intuitiveremoval of the sheath pair by a health professional, thereby reducingthe chances that the sheath pair are removed improperly.

Referring to FIGS. 8A-8C, methods for removing the sheath pair from thescaffold-balloon 10/12 by the health professional are now described.These illustrations refer to moving the sheath pair over the mandrel 8;however, a mandrel 8 is not necessary. The sheath pair 30/230 may besafely removed from the catheter assembly 2 without using a mandrel 8.

A sterilized and packaged catheter assembly with sheaths 20, 230positioned as shown in FIG. 8A typically includes the stiffening orstorage mandrel 8 in the catheter shaft 4 lumen to provide bendingstiffness for shaft 4. A distal end of the mandrel 8 has a curled end,or an extension/stop at the distal end (not shown), which is used tomanually withdraw the mandrel 8 from the catheter shaft 4 lumen bypulling the mandrel 8 towards the distal end 6 of the catheter assembly2. In the following example the sheaths 20, 230 are removed. Theproscribed steps preferably also include the act of removing the mandrel8 from the catheter shaft lumen by, e.g., simultaneously gripping theraised end 22, sheath 230 and mandrel 8.

First, the sheath 230 portion 240 is grabbed and pulled away from thescaffold-balloon 10/12 structure, which removes the constraining portion235 from the scaffold-balloon 10/12 structure. The sheath 230 may bewithdrawn or pulled away from the scaffold-balloon 10/12 in thefollowing manner. One hand grasps the portion 230; the other hand graspsthe catheter shaft 4 proximal of the scaffold 10 to hold the catheter 2stationary. The sheath 230 is pulled in the direction P (FIG. 8B). Whenthe ID junction 241 abuts the stepped end 22 of sheath 20, theconstraining portion 235 has cleared the scaffold. At this pointcontinued pulling of the sheath 230 will also remove the sheath 20 fromthe scaffold and eventually separate the sheath 20/230 from the catheter2. The raised end 22 therefore functions as an abutment for removingboth sheaths in a safe manner with minimal disruption to the crimpedscaffold.

As an alternative to the sheath 230 formed from a single piece oftubing, in FIG. 7D there is a sheath 250 made from two tubes ofdifferent diameter fastened together. A sheath 250 has a first portion252 that applies the radial constraint to the scaffold and a secondportion 255 for removal of the first portion 252 from the scaffold. Thesheath 250 may be positioned and removed from the sheath 20 in the samemanner as described above for sheath 230. As with sheath 230 there isthe ID junction 251 for abutment with the end 22 when the sheath 250 isremoved.

In a preferred method of making sheath 20, the raised ends are made withthe sheath 30 and 230 over the tube forming the sheath 20. The raisedends retain the sheath 30 on the sheath 20. Since the one-piece sheath30/230 is disposed over the tube forming the sheath 20 prior to formingthe raised ends, the overall length of the one-piece sheath 30/230 ispreferably limited to less than the overall length of the sheath 20 (sothat for manufacturing reasons the ends can be accessed to form theraised ends). However, by using a two-piece sheath 250 the overalllength L250 of the finished sheath can be significantly longer than thesheath 20, since the raised ends of sheath 20 can be formed with theportion 252 on sheath 20 but prior to the tube portion 255 attached at254 (FIG. 7D). According to the embodiment of FIG. 7D the sheath 250 maypreferably either have a longer length L250 than sheath 20 length, alength about the same as sheath 20 or shorter length.

According to a method of crimping, a crimping process at or near to aglass transition temperature of the polymer of the scaffold 10 isconducted as explained in U.S. application Ser. No. 13/644,347 (docketno. 62571.675) including FIGS. 3A and 4A. Before placing a two-piecesheath as described above, a temporary sheath may be formed with slitsor weakened areas that will facilitate a tearing away of the sheath whenit is attached to the scaffold. Examples of such a sheath is describedin U.S. application Ser. No. 13/708,638 (docket no. 62571.676) as shownin FIGS. 2, 3A-3E and 4.

The above description of illustrated embodiments of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the claims should not beconstrued to limit the invention to the specific embodiments disclosedin the specification. Rather, the scope of the invention is to bedetermined entirely by the claims, which are to be construed inaccordance with established doctrines of claim interpretation.

1. An apparatus, comprising: a catheter comprising a scaffold crimped toa balloon of the catheter and a sheath comprising a protecting portionand a constraining portion disposed over the scaffold, wherein theprotecting portion is located between the constraining portion and thescaffold; a tube containing at least a portion of the catheter, the tubecomprising a member disposed within the tube and configured to abut theconstraining portion when the catheter is withdrawn from the tube, suchthat the member abutting the constraining portion displaces theconstraining portion away from the scaffold as the catheter is withdrawnfrom the tube; and wherein the catheter is configured for beingintroduced into a body only after the sheath is removed from thescaffold. 2-20. (canceled)
 21. The apparatus of claim 1, wherein themember comprises a clip, rim or flange attached to the tube, or themember is a portion of the tube.
 22. The apparatus of claim 1, whereinthe member is a clip attached to an exterior surface of the tube, theclip comprises a protrusion that penetrates the bore of the tube, andthe constraining portion abuts the protrusion as the catheter iswithdrawn from the tube.
 23. The apparatus of claim 22, wherein the clipincludes two halves connected to each other by a living hinge, each halfforming a protrusion received in respective through holes when the clipis attached to the exterior surface, and both protrusions penetrate thebore of the tube
 24. The apparatus of claim 1, wherein the member is atube portion or a rim formed in the tube, wherein the constrainingportion abuts the tube portion as the catheter is being withdrawn fromthe tube.
 25. The apparatus of claim 1, wherein the member is a neck ofthe tube, wherein the constraining portion abuts the neck as thecatheter is withdrawn from the tube.
 26. The apparatus of claim 25,wherein the neck is located at a proximal end of the tube and adjacent ahub or handle portion of the catheter.
 27. The apparatus of claim 1,wherein the sheath is a one-piece sheath or a two-piece sheath.
 28. Theapparatus of claim 1, wherein the tube is a two-piece tube comprising afirst tube configured to contain the scaffold and the sheath therein,and a second tube configured for mating with the first tube andcomprising the member.
 29. An apparatus, comprising: a cathetercomprising a scaffold crimped to a balloon of the catheter, and a sheathcomprising a protecting portion and a constraining portion disposed overthe scaffold, wherein the protecting portion is located between theconstraining portion and the scaffold; a tube containing a substantialportion of the catheter and comprising means for removing theconstraining portion from the scaffold when the catheter is removed fromthe tube; wherein the catheter is configured for being introduced into abody only after the sheath is removed from the scaffold.
 30. Theapparatus of claim 29, wherein a proximal end of the tube is adjacent ahub or handle portion of the catheter.
 31. An apparatus, comprising: acatheter and a scaffold crimped to a balloon of the catheter; a sheathcovering the scaffold and configured for being removed therefrom beforethe catheter is introduced into a body; a tube containing the catheterwithin a lumen defined by a first tube portion and a second tube portionattached to the first tube portion; the first tube portion comprising afirst clearance and a second clearance portions of walls of the firsttube portion lumen, wherein a length of the second clearance is lessthan a length of the first clearance; the scaffold and the sheath iscontained in the second tube portion; and the sheath is configured forbeing removed from the tube by the second clearance interfering with thesheath as the catheter is removed from the tube.
 32. The apparatus ofclaim 31, wherein the second clearance portion is located at an end ofthe first tube portion and the apparatus is configured such that thecatheter is removed from the end of the first tube portion, therebycausing removal of the sheath from the catheter when the catheter isremoved from the end of the first tube portion.
 33. The apparatus ofclaim 31, wherein the catheter comprises a hub or handle portion, andthe first tube portion has a first end and a second end, wherein thefirst end is adjacent the catheter hub or handle portion, the first endcomprises the second diameter clearance portion, and the second tubeportion is connected to the first tube portion at the second end. 34.The apparatus of claim 31, wherein a majority of the catheter iscontained within the second tube portion.
 35. The apparatus of claim 31,wherein the sheath comprises a protecting portion and a constrainingportion disposed over the scaffold, wherein the protecting portion islocated between the constraining portion and the scaffold.
 36. Theapparatus of claim 35, wherein the sheath is a one-piece sheath.
 37. Theapparatus of claim 35, wherein the sheath is a two-piece sheathcomprising a first sheath and a second sheath disposed over the firstsheath, wherein the first sheath is the protecting portion and thesecond sheath is the constraining portion.
 38. The apparatus of claim31, wherein the first tube portion and the second tube portion areseparate tubes that are attached and held together by any combination ofa sleeve, tape and clip.